The International Maritime Organization (IMO) has a policy of incrementally strengthening sulfur concentration restrictions in fuel oil in order to reduce sulfur oxides (SOx) contained in the exhaust gases of ships, and intends to finally impose a restriction of no more than 0.5% sulfur concentration, applicable to all sea areas. Therefore, ship operators need to take measures such as using low-sulfur-content fuel, or installing an exhaust gas processing device in the main engine.
A scrubber which reduces the concentration of harmful material in the exhaust gas by passing the exhaust gas through seawater is known as an exhaust gas processing device for a ship (see, for example, PTL 1 and PTL 2).